Answer:
D € [0, 16]
Step-by-step explanation:
if you were looking at this from a purely mathematical sense the domain would be infinite but here the number n can't be negative because it is impossible to make negative candles and the function A(n) can't be negative because you can't have negative wax.
it would help to draw the function and look for the values of n in the first quadrant (where both n and A(n) are positive) and that is the domain.
the most candles you can make is 800-50n = 0
n = 800/50 = 16
the domain is
D € [0, 16]